1. Field of the Invention
This invention relates to apparatus for processing coins. The invention relates more particularly to an improved arrangement for establishing a reduced pressure in a chamber of a coin processing apparatus.
2. Description of the Prior Art
A coin processing apparatus having a sorting drum arrangement is known wherein an apertured, sorting drum rotates in a stationary housing. Coins being processed are deposited in the rotating drum, and, after tumbling in the drum near a lower location of the housing, seat themselves in the drum apertures. A reduced pressure in an adjacent chamber between the housing and the drum establishes a restraining force on the seated coins. This force maintains the seated coins in the apertures as they are rotatably transported by the drum from a lower location to an elevated station in the housing. The coins are then automatically transferred to a coin receptacle at the elevated station for processing. An apparatus of this type is disclosed and is claimed in U.S. Pat. No. 3,707,244 which is assigned to the assignee of this invention.
Coins being transported by the drum experience varying forces during transport. Initially, as the coins are deposited in the drum, they tumble and become seated in drum apertures. Gravitational force operates to restrain coins in apertures thus seated. However, as the drum rotates, the spatial attitude of the coin and its seat changes until finally they are rotated to an overhead station at which location the gravitational force, now acting to dislode a seated coin from an aperture is greatest. A restraining vacuum force which is applied to a seated coin should therefore be of sufficient magnitude to maintain a coin seated at its different attitudes during transport.
Although it may initially appear that the application of a uniform, relatively high vacuum at both elevated and lower housing locations would, in general, provide the desired coin restraint, in practice this is found not to be the case. The seating characteristic of the coin in an aperture must also be considered and this factor renders it preferable to establish a relatively lower vacuum force on the seated coin at lower housing locations. A relatively high vacuum at a lower housing location is accompanied by increased air leakage about a seated coin. At times, this leakage is sufficiently large to undesirably cause a second coin to be simultaneously restrained and to be transported in piggyback fashion with the seated coin. To avoid this potential problem, the vacuum restraining force is preferably relatively low at lower housing locations and increases in magnitude as the coin rotates from the lower housing location to an upper location. For example, the vacuum established may range between about 1 to 2 inches of water at lower housing locations to between about 8 to 9 inches of water in the vicinity of upper housing locations. Moreover, while coins of different size having different surface areas should theoretically be restrained under the same vacuum, in practice it is also found that coins of relatively larger area require a relatively larger vacuum restraining force. As a result, pressures established in the apparatus to restrain one size coin will not under all circumstances be sufficient to restrain relatively larger size coins. Consequently, established pressures can not generally be used interchangeabely with coins of different size and vacuum readjustments may be necessary when processing coins of different sizes.
The aforementioned differential pressure requirements have been satisfied in part by the use of a stationary baffle plate. This plate is positioned in the chamber and establishes a constriction therein which separates the chamber into a relatively low pressure sector and a relatively higher pressure sector. In view of the desired differential pressures, the positioning of the baffle in the chamber is important and should be accomplished with a relatively high degree of care and accuracy. This need to carefully locate a stationary baffle plate imposes constraints on the design of the apparatus and thus increases the cost of fabrication and the intial set up of the apparatus. Moreover, in view of the processing of coins of different sizes and other variations encountered in the operation of the apparatus which result in pressure changes, e.g., variations in the source vacuum, variations in the dimensions of manufactured parts with wear, etc. the stationary baffle must at times be relocated in order to com- pensate for these factors. Relocation of the stationary baffle plate, however, has in the past required disassembly of the apparatus and is therefore relatively time consuming and expensive.